Several studies suggest possible serotonergic involvement in the neurobiology of alcoholism. To evaluate this possibility we administered the serotonin agonist m-chlorophenylpiperazine (m-CPP) to alcoholics and controls. By observing the drug-induced behavioral effects and measuring changes in prolactin, cortisol and ACTH, we hope to make inferences about post-synaptic serotonin function in subjects with alcoholism. Our results indicate alcoholics with an early onset of drinking-related problems (Type II) are statistically more likely to "desire a drink of alcohol" following IV administration of m-CPP than late onset alcoholics (Type I) or controls. This desire does not appear to be the result of drug-induced anxiety.